Conventionally, there have been proposed various display devices called head-up display devices which project display images and display virtual images on a transflective surface called combiner or windshield of a vehicle (for example, PTL 1). As shown in FIG. 1, a head-up display device 1 is disposed in a dashboard of the vehicle, and display light N projected by the head-up display device 1 is reflected by a windshield 2a, so that a user 3 can visually recognize a virtual image V superimposed on a landscape.